Climate Change 5 Million Years Ago Coincided With More Mediterranean Volcanoes

As the Mediterranean Sea dried up during the Messinian Age and removed downward pressure on the Earth's surface, volcanic activity increased in the region.

Research that makes a convincing case for the disappearance of water from the primordial Mediterranean Sea also holds a potentially explosive lesson about climate change.

An international team of scientists found that volcanic eruptions and similar activity more than doubled during the so-called Messinian Age around 5.3-6 million years ago when the Strait of Gibraltar became a barrier that separated the Mediterranean Sea from the Atlantic Ocean.

“By removing some of the load on the Earth’s surface, you decrease the pressure at depth,” said Pietro Sternai, a geodynamics researcher at the University of Geneva and lead author on a study on the team’s findings published in the journal Nature Geoscience.

Debates have sprung up about fate of the Mediterranean Sea in the Messinian Era.

Some like Sterni believed it evaporated, as evidenced by deep layers of salt on the bottom on the Mediterranean today, a trace of what could have been left behind. Deep canyons on the bottom of the sea also suggest big rivers once carved their way through the area. The recent discovery of hominids on Crete almost six million years ago also would indicate they somehow walked to the ancient island.

Others argued the sea didn’t dry up but became stagnant and salty like the Dead Sea today.

Sternai said his modeling showed the evaporation that occurred over the course of 100,000 years removed 1.2 miles of sea level in the Mediterranean, or 1,450 pounds-per-square-inch of pressure at the sea bottom. That dry period coincided with increased volcanic activity. The weight of the water actually pushed the Earth down, suppressing the magma underneath.

“We are used to thinking in terms of volcanos and CO2 and how they affect climate,” he said. “This is very common. What is less common to think about is that the climate, by changing the distribution of pressure on the surface, affects the production of magma and therefore volcanism.”

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The same dynamic could be occurring today as climate change melts the glaciers in the North and South Poles, removing pressure on the glowing seams and fissures below. Consider how eruptions of Iceland’s volcanoes have spiked as that country’s glacial ice has melted.

“There is a lot of debate going on about the worldwide increase in volcanic activity due to the melting of the continental ice sheets,” he said. “In this interglacial period when we are living, you are basically unloading a continent.”

Conversely, oceanic volcanoes were erupting less frequently recently as melting glacial ice raised sea levels and more water bore down on the ocean floor. “There is a balance between the continental and the oceanic volcanic activity,” he said. “When you increase one there should be a decrease in the other.”

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Sternai next wants to conduct a detailed study on Giglio, a volcanic Italian island off the coast of Tuscany, to learn more about how the volcanos erupted without the water sitting on top of them.

“The aim would be to see whether the volume and not just the number of eruptions show any trend that we can recognize and correlate to the salinity,” he said. “That would be an interesting objective.”

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